9. 2 Area and Circumference of Circles

Front

What is the formula for the area of a circle?

Back

The area (A) of a circle is calculated using the formula A = πr², where r is the radius of the circle.

Front

How do you calculate the circumference of a circle?

Back

The circumference (C) of a circle is calculated using the formula C = 2πr or C = πd, where r is the radius and d is the diameter.

Front

If a circle has a diameter of 10 meters, what is its radius?

Back

The radius (r) of a circle is half of the diameter. Therefore, if the diameter is 10 meters, the radius is 5 meters.

Front

What is the value of π (pi) to two decimal places?

Back

The value of π (pi) is approximately 3.14.

Front

What is the area of a circle with a radius of 3 meters?

Back

Using the formula A = πr², the area is A = π(3)² = 28.26 m².

Front

How do you convert diameter to radius?

Back

To convert diameter to radius, divide the diameter by 2.

Front

What is the circumference of a circle with a radius of 4 inches?

Back

Using the formula C = 2πr, the circumference is C = 2π(4) = 25.13 inches.

Front

If the area of a circle is 50.24 cm², what is the radius?

Back

To find the radius, use the formula A = πr². Rearranging gives r = √(A/π). Thus, r = √(50.24/π) ≈ 4 cm.

Front

What is the relationship between diameter and circumference?

Back

The circumference of a circle is directly proportional to its diameter, expressed as C = πd.

Front

What is the area of a circle with a diameter of 12 meters?

Back

First, find the radius: r = diameter/2 = 6 meters. Then, A = πr² = π(6)² = 113.10 m².